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  <div class="question_difficulty">
   难度：Medium
  </div>
  <div>
   <h1 class="question_title">
    991. Array of Doubled Pairs
   </h1>
   <p>
    Given an array of integers
    <code>
     A
    </code>
    &nbsp;with even length, return
    <code>
     true
    </code>
    if and only if it is possible to reorder it such that
    <code>
     A[2 * i + 1] = 2 * A[2 * i]
    </code>
    for every
    <code>
     0 &lt;=&nbsp;i &lt; len(A) / 2
    </code>
    .
   </p>
   <p>
    &nbsp;
   </p>
   <div>
    <div>
     <div>
      <ol>
      </ol>
     </div>
    </div>
   </div>
   <div>
    <p>
     <strong>
      Example 1:
     </strong>
    </p>
    <pre>
<strong>Input: </strong><span id="example-input-1-1">[3,1,3,6]</span>
<strong>Output: </strong><span id="example-output-1">false</span>
</pre>
    <div>
     <p>
      <strong>
       Example 2:
      </strong>
     </p>
     <pre>
<strong>Input: </strong><span id="example-input-2-1">[2,1,2,6]</span>
<strong>Output: </strong><span id="example-output-2">false</span>
</pre>
     <div>
      <p>
       <strong>
        Example 3:
       </strong>
      </p>
      <pre>
<strong>Input: </strong><span id="example-input-3-1">[4,-2,2,-4]</span>
<strong>Output: </strong><span id="example-output-3">true</span>
<strong>Explanation: </strong><span id="example-output-3">We can take two groups, [-2,-4] and [2,4] to form [-2,-4,2,4] or [2,4,-2,-4].</span>
</pre>
      <div>
       <p>
        <strong>
         Example 4:
        </strong>
       </p>
       <pre>
<strong>Input: </strong><span id="example-input-4-1">[1,2,4,16,8,4]</span>
<strong>Output: </strong><span id="example-output-4">false</span>
</pre>
       <p>
        &nbsp;
       </p>
       <p>
        <strong>
         Note:
        </strong>
       </p>
       <ol>
        <li>
         <code>
          0 &lt;= A.length &lt;= 30000
         </code>
        </li>
        <li>
         <code>
          A.length
         </code>
         is even
        </li>
        <li>
         <code>
          -100000 &lt;= A[i] &lt;= 100000
         </code>
        </li>
       </ol>
      </div>
     </div>
    </div>
   </div>
  </div>
  <div>
   <h1 class="question_title">
    991. 二倍数对数组
   </h1>
   <p>
    给定一个长度为偶数的整数数组&nbsp;
    <code>
     A
    </code>
    ，只有对&nbsp;
    <code>
     A
    </code>
    &nbsp;进行重组后可以满足 &ldquo;对于每个
    <code>
     0 &lt;=&nbsp;i &lt; len(A) / 2
    </code>
    ，都有
    <code>
     A[2 * i + 1] = 2 * A[2 * i]
    </code>
    &rdquo;&nbsp;时，返回
    <code>
     true
    </code>
    ；否则，返回
    <code>
     false
    </code>
    。
   </p>
   <p>
    &nbsp;
   </p>
   <p>
    <strong>
     示例 1：
    </strong>
   </p>
   <pre><strong>输入：</strong>[3,1,3,6]
<strong>输出：</strong>false
</pre>
   <p>
    <strong>
     示例 2：
    </strong>
   </p>
   <pre><strong>输入：</strong>[2,1,2,6]
<strong>输出：</strong>false
</pre>
   <p>
    <strong>
     示例 3：
    </strong>
   </p>
   <pre><strong>输入：</strong>[4,-2,2,-4]
<strong>输出：</strong>true
<strong>解释：</strong>我们可以用 [-2,-4] 和 [2,4] 这两组组成 [-2,-4,2,4] 或是 [2,4,-2,-4]</pre>
   <p>
    <strong>
     示例 4：
    </strong>
   </p>
   <pre><strong>输入：</strong>[1,2,4,16,8,4]
<strong>输出：</strong>false
</pre>
   <p>
    &nbsp;
   </p>
   <p>
    <strong>
     提示：
    </strong>
   </p>
   <ol>
    <li>
     <code>
      0 &lt;= A.length &lt;= 30000
     </code>
    </li>
    <li>
     <code>
      A.length
     </code>
     &nbsp;为偶数
    </li>
    <li>
     <code>
      -100000 &lt;= A[i] &lt;= 100000
     </code>
    </li>
   </ol>
  </div>
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